Radial runout, in tires and wheels on vehicles, is a measure of deviation from a perfect circle. Radial and lateral runout can create vibration in a moving vehicle. These vibrations can increase driver fatigue, increase vehicle wear and cause cargo damage. Radial runout is generally caused by an out of round tire and/or wheel, and/or an imperfectly centered wheel on a vehicle hub.
Prior known run-out gauges mount a dial indicator with the plunger against the tire tread. When the tire is rotated with these gauges, a vertical force is exerted against the plunger, so the plunger can bind and the measurement can be inaccurate.